Low cost antennas using conductive plastics or conductive composites

ABSTRACT

Low cost antennas formed of a conductive loaded resin-based material. The conductive loaded resin-based material comprises conductor fibers or conductor particles in a resin or plastic host wherein the ratio of the weight of the conductor fibers or conductor particles to the weight of the resin or plastic host is between about 0.20 and 0.40. The conductive fibers can be stainless steel, nickel, copper, silver, or the like. The antenna elements can be formed using methods such as injection molding or extrusion. Virtually any antenna fabricated by conventional means such as wire, strip-line, printed circuit boards, or the like can be fabricated using the conductive loaded resin-based materials. The conductive loaded resin-based material used to form the antenna elements can be in the form of a thin flexible woven fabric which can readily cut to the desired shape.

[0001] This patent application is a Continuation In Part of applicationSer. No. 10/075,778, filed Feb. 14, 2002.

BACKGROUND OF THE INVENTION

[0002] (1) Field of the Invention

[0003] This invention relates to antennas formed of conductive loadedresin-based materials comprising micron conductive powders or micronconductive fibers.

[0004] (2) Description of the Related Art

[0005] Antennas are an essential part of electronic communicationsystems that contain wireless links. Low cost antennas offer significantadvantages for these systems.

[0006] U.S. Pat. No. 5,771,027 to Marks et al. describes a compositeantenna having a grid comprised of electrical conductors woven into thewarp of a resin reinforced cloth forming one layer of a multi-layerlaminate structure of an antenna.

[0007] U.S. Pat. No. 6,249,261 B1 to Solberg, Jr. et al. describes adirection-finding material constructed from polymer composite materialswhich are electrically conductive.

SUMMARY OF THE INVENTION

[0008] Antennas are essential in any electronic systems containingwireless links. Such applications as communications and navigationrequire reliable sensitive antennas. Antennas are typically fabricatedfrom metal antenna elements in a wide variety of configurations.Lowering the cost of antenna materials or production costs infabrication of antennas offers significant advantages for anyapplications utilizing antennas.

[0009] It is a principle objective of this invention to provide antennasfabricated from conductive loaded resin-based materials.

[0010] It is another principle objective of this invention to provideantennas having two antenna elements fabricated from conductive loadedresin-based materials.

[0011] It is another principle objective of this invention to provideantennas having an antenna element and a ground plane fabricated fromconductive loaded resin-based materials.

[0012] It is another principle objective of this invention to provide amethod of forming antennas from conductive loaded resin-based materials.

[0013] These objectives are achieved by fabricating the antenna elementsand ground planes from conductive loaded resin-based materials. Thesematerials are resins loaded with conductive materials to provide aresin-based material which is a conductor rather than an insulator. Theresins provide the structural material which, when loaded with micronconductive powders or micron conductive fibers, become composites whichare conductors rather than insulators.

[0014] Antenna elements are fabricated from the conductive loadedresins. Almost any type of antenna can be fabricated from the conductiveloaded resin-based materials, such as dipole antennas, monopoleantennas, planar antennas or the like. These antennas can be tuned to adesired frequency range.

[0015] The antennas can be molded or extruded to provide the desiredshape. The conductive loaded resin-based materials can be cut, injectionmolded, over-molded, laminated, extruded, milled or the like to providethe desired antenna shape and size. The antenna characteristics dependon the composition of the conductive loaded resin-based materials, whichcan be adjusted to aid in achieving the desired antenna characteristics.Virtually any antenna fabricated by conventional means such as wire,strip-line, printed circuit boards, or the like can be fabricated usingthe conductive loaded resin-based materials.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 shows a perspective view of a dipole antenna formed from aconductive loaded resin-based material.

[0017]FIG. 2A shows a front view of the dipole antenna of FIG. 1 showinginsulating material between the radiating antenna element and a groundplane.

[0018]FIG. 2B shows a front view of the dipole antenna of FIG. 1 showinginsulating material between both the radiating antenna element and thecounterpoise antenna element and a ground plane.

[0019]FIG. 2C shows an amplifier inserted between the radiating antennaelement and the coaxial cable center conductor for the dipole antenna ofFIG. 1.

[0020]FIG. 3 shows a segment of an antenna element formed from aconductive loaded resin-based material showing a metal insert forconnecting to conducting cable elements.

[0021]FIG. 4A shows a perspective view of a patch antenna comprising aradiating antenna element and a ground plane with the coaxial cableentering through the ground plane.

[0022]FIG. 4B shows a perspective view of a patch antenna comprising aradiating antenna element and a ground plane with the coaxial cableentering between the ground plane and the radiating antenna element.

[0023]FIG. 5 shows an amplifier inserted between the radiating antennaelement and the coaxial cable center conductor for the patch antenna ofFIGS. 4A and 4B.

[0024]FIG. 6 shows a perspective view of a monopole antenna formed froma conductive loaded resin-based material.

[0025]FIG. 7 shows a perspective view of a monopole antenna formed froma conductive loaded resin-based material with an amplifier between theradiating antenna element and the coaxial cable center conductor.

[0026]FIG. 8A shows a top view of an antenna having a single L shapedantenna element formed from a conductive loaded resin-based material.

[0027]FIG. 8B shows a cross section view of the antenna element of FIG.8A taken along line 8B-8B′ of FIG. 8A.

[0028]FIG. 8C shows a cross section view of the antenna element of FIG.8A taken along line 8C-8C′ of FIG. 8A.

[0029]FIG. 9A shows a top view of an antenna formed from a conductiveloaded resin-based material embedded in an automobile bumper.

[0030]FIG. 9B shows a front view of an antenna formed from a conductiveloaded resin-based material embedded in an automobile bumper formed ofan insulator such as rubber.

[0031]FIG. 10A shows a schematic view of an antenna formed from aconductive loaded resin-based material embedded in the molding of avehicle window.

[0032]FIG. 10B shows a schematic view of an antenna formed from aconductive loaded resin-based material embedded in the plastic case of aportable electronic device.

[0033]FIG. 11 shows a cross section view of a conductive loadedresin-based material comprising a powder of conductor materials.

[0034]FIG. 12 shows a cross section view of a conductive loadedresin-based material comprising conductor fibers.

[0035]FIG. 13 shows a simplified schematic view of an apparatus forforming injection molded antenna elements.

[0036]FIG. 14 shows a simplified schematic view of an apparatus forforming extruded antenna elements.

[0037]FIG. 15A shows a top view of fibers of conductive loadedresin-based material webbed into a conductive fabric.

[0038]FIG. 15B shows a top view of fibers of conductive loadedresin-based material woven into a conductive fabric.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] The following embodiments are examples of antennas fabricatedusing conductive loaded resin-based materials. In some of the examplesground planes are also used and these ground planes can be formed ofeither conductive loaded resin-based materials or metals. The use ofthese conductive loaded resin-based materials in antenna fabricationsignificantly lowers the cost of materials and manufacturing processesused in the assembly antennas and the ease of forming these materialsinto the desired shapes. These materials can be used to form eitherreceiving or transmitting antennas. The antennas and/or ground planescan be formed using methods such as injection molding, overmolding, orextrusion of the conductive loaded resin-based materials.

[0040] The conductive loaded resin-based materials typically but notexclusively have a conductivity of between about 5 and 25 ohms persquare. The antenna elements, used to form the antennas, are formed ofthe conductive loaded resin-based materials and can be formed usingmethods such as injection molding, overmolding, or extrusion. Theantenna elements can also be stamped to produce the desired shape. Theconductive loaded resin-based material antenna elements can also cut ormilled as desired.

[0041] The conductive loaded resin-based materials comprise micronconductive powders or fibers loaded in a structural resin. The micronconductive powders are formed of metals such as nickel, copper, silveror the like. The micron conductive fibers can be nickel plated carbonfiber, stainless steel fiber, copper fiber, silver fiber, or the like.The structural material is a material such as a polymer resin.Structural material can be, here given as examples and not as anexhaustive list, polymer resins produced by GE PLASTICS, Pittsfield,Mass., a range of other plastics produced by GE PLASTICS, Pittsfield,Mass., a range of other plastics produced by other manufacturers,silicones produced by GE SILICONES, Waterford, N.Y., or other flexibleresin-based rubber compounds produced by other manufacturers. Theresin-based structural material loaded with micron conductive powders orfibers can be molded, using a method such as injection molding,overmolding, or extruded to the desired shape. The conductive loadedresin-based materials can be cut or milled as desired to form thedesired shape of the antenna elements. The composition of the compositematerials can affect the antenna characteristics and must be properlycontrolled. The composite could also be in the family of polyesters withwoven or webbed micron stainless steel fibers or other micron conductivefibers forming a cloth like material which, when properly designed inmetal content and shape, can be used to realize a very high performancecloth antenna. Such a cloth antenna could be embedded in a personsclothing as well as in insulating materials such as rubber or plastic.The woven or webbed conductive cloths could also be laminated tomaterials such as Teflon, FR-4, or any resin-based hard material.

[0042] Refer now to FIGS. 1-10B for examples of antennas fabricatedusing conductive loaded resin-based materials. These antennas can beeither receiving or transmitting antennas. FIG. 1 shows a perspectivedrawing of a dipole antenna with a radiating antenna element 12 and acounterpoise antenna element 10 formed from conductive loadedresin-based materials. The antenna comprises a radiating antenna element12 and a counterpoise antenna element 10 each having a length 24 and arectangular cross section perpendicular to the length 24. The length 24is greater than three multiplied by the square root of the crosssectional area. The center conductor 14 of a coaxial cable 50,iselectrically connected to the radiating antenna element 12 using a metalinsert 15 formed in the radiating antenna element 12. The shield 52 ofthe coaxial cable 50 is connected to the counterpoise antenna element 10using a metal insert formed in the counterpoise antenna element 10. Themetal insert in the counterpoise antenna element 10 is not visible inFIG. 1 but is the same as the metal insert 15 in the radiating antennaelement 12. The length 24 is a multiple of a quarter wavelength of theoptimum frequency of detection or transmission of the antenna. Theimpedance of the antenna at resonance should be very nearly equal to theimpedance of the coaxial cable 50 to assure maximum power transferbetween cable and antenna.

[0043]FIG. 3 shows a detailed view of a metal insert 15 formed in asegment 11 of an antenna element. The metal insert can be copper orother metal. A screw 17 can be used in the metal insert 15 to aid inelectrical connections. Soldering or other electrical connection methodscan also be used.

[0044]FIG. 1 shows an example of a dipole antenna with the radiatingantenna element 12 placed on a layer of insulating material 22, which isplaced on a ground plane 20, and the counterpoise antenna element 10placed directly on the ground plane 20. The ground plane 20 is optionaland if the ground plane is not used the layer of insulating material 22may not be necessary. As another option the counterpoise antenna element10 can also be placed on a layer of insulating material 22, see FIG. 2A.If the ground plane 20 is used it can also be formed of the conductiveloaded resin-based materials.

[0045]FIG. 2A shows a front view of the dipole antenna of FIG. 1 for theexample of an antenna using a ground plane 20, a layer of insulatingmaterial 22 between the radiating antenna element 12 and the groundplane 20, and the counterpoise antenna element 10 placed directly on theground plane 20. FIG. 2B shows a front view of the dipole antenna ofFIG. 1 for the example of an antenna using a ground plane 20 and a layerof insulating material 22 between both the radiating antenna element 12and the counterpoise antenna element 10.

[0046] As shown in FIG. 2C, an amplifier 72 can be inserted between thecenter conductor 14 of the coaxial cable and the radiating antennaelement 12. A wire 70 connects metal insert 15 in the radiating antennaelement 12 to the amplifier 72. For receiving antennas the input of theamplifier 72 is connected to the radiating antenna element 12 and theoutput of the amplifier 72 is connected to the center conductor 14 ofthe coaxial cable 50. For transmitting antennas the output of theamplifier 72 is connected to the radiating antenna element 12 and theinput of the amplifier 72 is connected to the center conductor 14 of thecoaxial cable 50.

[0047] In one example of this antenna the length 24 is about 1.5 incheswith a square cross section of about 0.09 square inches. This antennahad a center frequency of about 900 MHz.

[0048]FIGS. 4A and 4B show perspective views of a patch antenna with aradiating antenna element 40 and a ground plane 42 formed fromconductive loaded resin-based materials. The antenna comprises aradiating antenna element 40 and a ground plane 42 each having the shapeof a rectangular plate with a thickness 44 and a separation between theplates 46 provided by insulating standoffs 60. The square root of thearea of the rectangular square plate forming the radiating antennaelement 40 is greater than three multiplied by the thickness 44. In oneexample of this antenna wherein the rectangular plate is a square withsides of 1.4 inches and a thickness of 0.41 inches the patch antennaprovided good performance at Global Position System, GPS, frequencies ofabout 1.5 MHz.

[0049]FIG. 4A shows an example of the patch antenna where the coaxialcable 50 enters through the ground plane 42. The coaxial cable shield 52is connected to the ground plane 42 by means of a metal insert 15 in theground plane. The coaxial cable center conductor 14 is connected to theradiating antenna element 40 by means of a metal insert 15 in theradiating antenna element 40. FIG. 4B shows an example of the patchantenna where the coaxial cable 50 enters between the radiating antennaelement 40 and the ground plane 42. The coaxial cable shield 52 isconnected to the ground plane 42 by means of a metal insert 15 in theground plane 42. The coaxial cable center conductor 14 is connected tothe radiating antenna element 40 by means of a metal insert 15 in theradiating antenna element 40.

[0050] As shown in FIG. 5 an amplifier 72 can be inserted between thecoaxial cable center conductor 14 and the radiating antenna element 40.A wire 70 connects the amplifier 72 to the metal insert 15 in theradiating antenna element 40. For receiving antennas the input of theamplifier 72 is connected to the radiating antenna element 40 and theoutput of the amplifier 72 is connected to the center conductor 14 ofthe coaxial cable 50. For transmitting antennas the output of theamplifier 72 is connected to the radiating antenna element 40 and theinput of the amplifier 72 is connected to the center conductor 14 of thecoaxial cable 50.

[0051]FIG. 6 shows an example of a monopole antenna having a radiatingantenna element 64, having a height 71, arranged perpendicular to aground plane 68. The radiating antenna element 64 and the ground plane68 are formed of conductive plastic or conductive composite materials. Alayer of insulating material 66 separates the radiating antenna element64 from the ground plane 68. The height 71 of the radiating antennaelement 64 is greater than three times the square root of the crosssectional area of the radiating antenna element 64. An example of thisantenna with a height 71 of 1.17 inches performed well at GPSfrequencies of about 1.5 GHz.

[0052]FIG. 7 shows an example of the monopole antenna described abovewith an amplifier 72 inserted between the center conductor 14 of thecoaxial cable 50 and the radiating antenna element 64. For receivingantennas the input of the amplifier 72 is connected to the radiatingantenna element 64 and the output of the amplifier 72 is connected tothe center conductor 14 of the coaxial cable 50. For transmittingantennas the output of the amplifier 72 is connected to the radiatingantenna element 64 and the input of the amplifier 72 is connected to thecenter conductor 14 of the coaxial cable 5.0.

[0053]FIGS. 8A, 8B, and 8C shows an example of an L shaped antennahaving a radiating antenna element 80 over a ground plane 98. Theradiating antenna element 80 and the ground plane 98 are formed ofconductive loaded resin-based materials. A layer of insulating material96 separates the radiating antenna element 64 from the ground plane 98.The radiating antenna element 80 is made up of a first leg 82 and asecond leg 84. FIG. 8A shows a top view of the antenna. FIG. 8B shows across section of the first leg 82. FIG. 8C shows a cross section of thesecond leg 84. FIGS. 8B and 8C show the ground plane 98 and the layer ofinsulating material 96. The cross sectional area of the first leg 82 andthe second leg 84 need not be the same. Antennas of this type may betypically built using overmolding technique to join the conductiveresin-based material to the insulating material.

[0054] Antennas of this type have a number of uses. FIGS. 9A and 9B showa dipole antenna, formed of conductive loaded resin-based materials,embedded in an automobile bumper 100, formed of insulating material. Thedipole antenna has a radiating antenna element 102 and a counterpoiseantenna element 104. FIG. 9A shows the top view of the bumper 100 withthe embedded antenna. FIG. 9B shows the front view of the bumper 100with the embedded antenna.

[0055] The antennas of this invention, formed of conductive loadedresin-based materials, can be used for a number of additionalapplications. Antennas of this type can be embedded in the molding of awindow of a vehicle, such as an automobile or an airplane. FIG. 10Ashows a schematic view of such a window 106. The antenna 110 can beembedded in the molding 108. Antennas of this type can be embedded inthe plastic housing, or be part of the plastic shell itself, of portableelectronic devices such as cellular phones, personal computers, or thelike. FIG. 10B shows a schematic view of a segment 112 of such a plastichousing with the antenna 110 embedded in the housing 112.

[0056] The conductive loaded resin-based material typically comprises apowder of conductor particles or a fiber of a conductor material in aresin or plastic host. FIG. 11 shows cross section view of an example ofconductor loaded resin-based material 212 having powder of conductorparticles 202 in a resin or plastic host 204. In this example thediameter 200 of the of the conductor particles 202 in the powder isbetween about 3 and 11 microns. FIG. 12 shows a cross section view of anexample of conductor loaded resin-based material 212 having conductorfibers 210 in a resin or plastic host 204. In this example the conductorfibers 210 have a diameter of between about 3 and 11 microns and alength of between about 5 and 10 millimeters. The conductors used forthese conductor particles 202 or conductor fibers 210 can stainlesssteel, nickel, copper, silver, or other suitable metals. These conductorparticles or fibers are embedded in a resin which in turn is embedded ina plastic host. As previously mentioned, the conductive loadedresin-based materials have a conductivity of between about 5 and 25 ohmsper square. To realize this conductivity the ratio of the weight of theconductor material, in this example the conductor particles 202 orconductor fibers 210, to the weight of the resin or plastic host 204 isbetween about 0.20 and 0.40.

[0057] Antenna elements formed from conductive loaded resin-basedmaterials can be formed in a number of different ways includinginjection molding or extrusion. FIG. 13 shows a simplified schematicdiagram of an injection mold showing a lower portion 230 and upperportion 231 of the mold. Uncured conductive loaded resin-based materialis injected into the mold cavity 237 through an injection opening 235and cured. The upper portion 231 and lower portion 230 of the mold arethen separated and the cured antenna element is removed.

[0058]FIG. 14 shows a simplified schematic diagram of an extruder forforming antenna elements using extrusion. Uncured conductive loadedresin-based material is placed in the cavity 239 of the extrusion unit234. A piston 236 or other means is then used to force the uncuredconductive loaded resin-based material through an extrusion opening 240which shapes the partially cured conductive loaded resin-based materialto the desired shape. The conductive loaded resin-based material is thenfully cured and is ready for use.

[0059] The conductive loaded resin based material can be formed intofibers which are woven or webbed into a conductive fabric. FIG. 15Ashows a webbed conductive fabric 230. FIG. 15B shows a webbed conductivefabric 232. This conductive fabric, 230 and/or 232, can be very thin andcut into desired shapes to form antenna elements. These antenna elementscan take the shape of a host and attached as desired.

[0060] Antennas formed from the conductive loaded resin-based materialscan be designed to work at frequencies from about 2 Kilohertz to about300 Gigahertz.

[0061] While the invention has been particularly shown and describedwith reference to the preferred embodiments thereof, it will beunderstood by those skilled in the art that various changes in form anddetails may be made without departing from the spirit and scope of theinvention.

What is claimed is:
 1. An antenna comprising: a number of antennaelements formed of a conductive loaded resin-based material, whereinsaid conductive loaded resin-based material comprises conductor fibersin a resin or plastic host and the ratio of the weight of said conductorfibers to the weight of said resin or plastic host is between about 0.20and 0.40; and electrical communication to and among said antennaelements. 2-30. (CANCELLED)
 31. A conductive composite, comprising: abase resin host; and micron conductor particles in said base resin hostwherein the ratio of the weight of said micron conductor particles tothe weight of said base resin host is between about 0.20 and 0.40,thereby forming a conductive loaded resin-based material.
 32. Theconductive composite of claim 31 wherein said micron conductor particleshave generally spherical shapes and diameters of between about 3 and 11microns.
 33. The conductive composite of claim 31 wherein said micronconductor particles are stainless steel, nickel, copper, or silver. 34.The conductive composite of claim 31 wherein said base resin host is apolymer resin.
 35. The conductive composite of claim 31 wherein saidconductive loaded resin-based material has a resistivity of betweenabout 5 and 25 ohms per square.
 36. The conductive composite of claim 31wherein said conductive loaded resin-based material can be used tofabricate antennas.
 37. The conductive composite of claim 31 whereinsaid conductive loaded resin-based material can be used to fabricateground planes.
 38. The conductive composite of claim 31 wherein saidconductive loaded resin-based material can be molded or extruded to formdesired shapes.
 39. The conductive composite of claim 31 wherein saidconductive loaded resin-based material can be cut or milled to formdesired shapes.
 40. The conductive composite of claim 31 wherein saidconductive loaded resin-based material can be formed into fibers whichcan be woven or webbed into a conductive fabric.
 41. A conductivecomposite, comprising: a base resin host; and micron conductor fibers insaid base resin host wherein the ratio of the weight of said micronconductor fibers to the weight of said base resin host is between about0.20 and 0.40, thereby forming a conductive loaded resin-based material.42. The conductive composite of claim 41 wherein said micron conductorfibers have diameters of between about 3 and 11 microns.
 43. Theconductive composite of claim 41 wherein said micron conductor fibershave lengths of between about 5 and 10 millimeters.
 44. The conductivecomposite of claim 41 wherein said micron conductor fibers are stainlesssteel, nickel, copper, silver, or nickel plated carbon.
 45. Theconductive composite of claim 41 wherein said base resin host is apolymer resin.
 46. The conductive composite of claim 41 wherein saidconductive loaded resin-based material has a resistivity of betweenabout 5 and 25 ohms per square.
 47. The conductive composite of claim 41wherein said conductive loaded resin-based material can be used tofabricate antennas.
 48. The conductive composite of claim 41 whereinsaid conductive loaded resin-based material can be used to fabricateground planes.
 49. The conductive composite of claim 41 wherein saidconductive loaded resin-based material can be molded or extruded to formdesired shapes.
 50. The conductive composite of claim 41 wherein saidconductive loaded resin-based material can be cut or milled to formdesired shapes.
 51. The conductive composite of claim 41 wherein saidconductive loaded resin-based material can be formed into fibers whichcan be woven or webbed into a conductive fabric.